For the provision of binders for drug coatings with a low residual monomer content, DE-B 2512238 teaches the use of a powder obtained by spray drying a polymer dispersion for producing coating solutions for these drug forms. With regard to the dispersions used for the spray drying, reference is made to DE 1090381, DE 1219175 and DE 2135073.
DE 3049179 A1 is an application of addition to DE 2512238 and relates to the use of a powder obtained by spray drying according to the teaching of the last-mentioned document in the form of an aqueous suspension, which additionally comprises a plasticizing agent, for producing coatings by thermogelation.
WO 00/05307 deals with the provision of coating and binding compositions for drug forms which comprise (meth)acrylate copolymers which have monomer radicals with tertiary amino groups, the intention being for simple dry or aqueous further processing to be possible. In addition, this document teaches a process in which (a) a copolymer of C1-C4-esters of (meth)acrylic acid and (meth)acrylate monomers which have tertiary ammonium groups, (b) a plasticizer and (c) an emulsifier with an HLB value of at least 14 are combined with one another and the coating or binding composition is produced therefrom by melting, pouring, spreading or spraying, where the copolymer (a) is incorporated in powder form with an average particle size from 1 to 40 μm. The processability achieved here is attributed to the provision of the copolymer (a) in powder form with an extremely small particle size.
WO 02/067906 relates to coating and binding compositions having improved water-vapor permeability compared with those described in WO 00/05307. Here, the coating and binding compositions are produced using a mixture which comprises (a) a copolymer of C1-C4-esters of (meth)acrylic acid and further (meth)acrylate monomers with functional tertiary ammonium groups in powder form having an average particle size from 1 to 40 μm, (b) an emulsifier with an HLB value of at least 14 and (c) a C12-C18-monocarboxylic acid or a C12-C18-hydroxyl compound.
WO 2004/019918 describes coating and binding compositions which correspond to those described in WO 00/05307 and WO 02/067906 as regards their composition.
According to U.S. Pat. No. 6,696,085 B2, a methacrylic acid copolymer type C is reportedly used as disintegrant. The methacrylic acid copolymer type C is an enteric polymer which is not soluble in the acidic pH range, but is water-soluble in the pH range of 7, as is present in the oral cavity. Besides a low fracture strength (<20N), the tablets have a high friability (>7%) and include a high proportion, in the region of 15% by weight, of coarsely particulate disintegrant. Consequently, they have low mechanical strength and, on account of the high proportion of coarsely particulate disintegrant, have an unpleasant sandy feel in the mouth.
EP88951 A2 describes a process for coating drugs using a water-dispersed coating composition based on emulsion polymers, where the coating compositions may be partially present in salt form. The coating compositions can also be obtained from redispersed powders, with the processes of spray drying and of freeze drying being specified as methods that are suitable in principle. However, in this connection, it is also stated that the freeze drying may also be able to be used at the lower limit of the range of suitable glass transition temperatures. Either powders obtained by freeze drying or a spray-dried product of 30% methacrylic acid and 70% methyl methacrylate, which has a high glass transition temperature on account of its composition, are specifically described.
WO 97/42255 describes the spray drying of polymer powders that can be redispersed in aqueous solution and comprise free acid- or base-carrying copolymers by spray drying, where, before the spray drying, the pH values of the dispersions have to be adjusted with the help of a buffer system.
EP 262326 A2 describes a process for producing a redispersible plastics polymer in which an aqueous dispersion of a copolymer of (meth)acrylic acid and (meth)acrylic acid esters with a minimum film-forming temperature below 60° C. and a dynamic glass transition temperature below 150° C. is spray dried such that the entry temperature of the drying gas is above the minimum film-forming temperature and below the glass transition temperature.
EP 901 787 A1 describes stabilized pharmaceutical preparations comprising active ingredients that are sensitive to decomposition by light or free radicals and which are coated with a coating composition which, besides metal oxides, basic substances and plasticizers, comprises free radical scavengers for stabilizing the active ingredients. Base materials that are mentioned for the coating compositions are all materials that are possible in principle, such as sugars, cellulose derivates, polyvinylpyrrolidones or (meth)acrylate polymers. It is also mentioned that the coating compositions can comprise aminoalkyl methacrylate polymers as slow-release polymers.
WO 2009/016258 discloses the production of the aqueous polymer dispersions of cationic polymers based on N,N-diethylaminoethyl methacrylate as are used according to the invention and the use thereof for the coating of drugs. Pulverulent coating compositions are only mentioned in quite general terms. On account of their low glass transition temperature, under certain circumstances, the polymers exhibit an undesired tendency towards agglomeration and therefore make high demands from a processing point of view. Special methods for stabilization for example against discoloration upon storage or for achieving release stability even upon prolonged storage or under stress are not mentioned.
There is a need for free-flowing pulverulent film coating compositions with good redispersibility in water which are suitable for pharmaceutical dosage forms which, even upon prolonged or thermally demanding storage, have no change in the release behavior of the film coatings and no discoloration. One requirement for such redispersed coating compositions is, inter alia, the generation of stable small-particle dispersions with narrow particle size distributions and the avoidance of coagulation. Furthermore, there is a need for polymer dispersions or polymer powders that can incorporate stabilizing substances such as antioxidants without adversely affecting the stability of the polymer dispersion or of the polymer powder and applications-related properties thereof. Also, a further problem is not only incorporating antioxidants which are in most cases sparingly soluble in water into the aqueous dispersion in a homogeneous manner, but also bringing them into contact to an adequate extent with the dispersed polymer particles to allow the water-insoluble antioxidants to migrate into the polymer particles since they are supposed to develop their effect therein. Consequently, there is a need for a process which transports a sparingly water-soluble substance into another phase via such a water phase. This problem is exacerbated by the fact that no plasticizer can be used which could act as entrainer since plasticizers make the conversion of such a preparation into a redispersible powder impossible on account of the onset of film formation.